The present invention relates to a method of cleaning pressurized containers having chemicals contained therein. Specifically, the present invention relates to a method of cleaning pressurized containers such as, for example, rail tank cars, mobile tanks or the like. Further, the chemicals may be any material stored under pressure that may be difficult to collect and dispose of due to the hazardous characteristics thereof. Preferably, however, the chemicals contained within the container comprise anhydrous ammonia.
It is, of course, generally known to store and/or transport chemicals having hazardous characteristics via pressurized containers. Further, it is also generally known to clean these containers using a variety of methods and systems. In the past, cleaning pressurized containers entailed venting excess gaseous material to the atmosphere. Further, unpressurized containers contained bottom hatches or valves for draining liquid chemicals. However, many hazardous chemicals escaped into the environment thereby causing health risks for humans, vegetation and wildlife. With the advent of environmental standards and compliance, however, venting or draining hazardous chemicals to the environment has generally become illegal. Today, the chemicals are typically routed to a flare to be incinerated or otherwise collected for disposal.
However, while some of the gases contained within the containers may be relatively easy to recover and dispose of by venting of the pressurized containers to a flare, it is difficult to remove all of the gases contained therein. Further, liquid product may remain inside a container after cleaning. Typical systems and methods of cleaning may involve injecting the container with a quantity of steam that may aid in bringing the liquid chemicals to the gaseous phase and removing the steam/gaseous chemical product combination for incineration or disposal. However, problems may occur using steam to remove chemicals from pressurized containers since steam may condense within the container forming liquid water or ice. The liquid water or ice may mask the presence of the chemicals from detectors. Further, the liquid water or ice may interfere with the removal of the chemicals from the container.
Another method of removal, especially for unpressurized containers having liquid therein, may include entering the container to manually remove the chemical. While this may be a relatively efficient and thorough way to remove the chemical from the container, it may be very dangerous, as it requires an individual to actually enter the container thereby exposing the individual to the chemicals contained therein. Further, by opening the container, there may be a significant risk that some of the chemicals may escape into the environment.
Therefore, an improved system of cleaning pressurized containers is necessary. Particularly, a system is needed that overcomes the problems associated with typical cleaning systems. Further, a system is needed that cleanly and efficiently moves chemical product from a pressurized container and transports the waste product to a proper disposal system such as a flare for incineration.
The present invention relates to a method of cleaning a pressurized container having anhydrous ammonia (xe2x80x9cAAxe2x80x9d) therein. More specifically, the present invention allows containers such as, for example, rail tank cars, to be cleaned safely and efficiently without risking exposure of the AA to people or the environment. The invention entails injecting heated and pressurized nitrogen gas into the container thereby purging the container of any chemical therein to form a nitrogen/AA mixture. The nitrogen/AA mixture may then be sent to a flare for incineration. Further, the heated nitrogen gas may aid in pulling the AA out of the container and transporting the chemical to the flare for incineration.
To this end, in an embodiment of the present invention, a method of cleaning a pressurized container is provided. The method comprises the steps of providing a pressurized container containing an amount of anhydrous ammonia wherein the container has inlet and outlet valves and injecting a quantity of heated nitrogen gas into the container to form a nitrogen/anhydrous ammonia mixture. The method further comprises venting the nitrogen/anhydrous ammonia mixture to the flare and repeating the injection of the container with heated nitrogen gas and venting the mixture to a flare until the concentration of anhydrous ammonia is less than or equal to about 10,000 ppm.
In an embodiment of the present invention, the method comprises the steps of providing a natural gas inlet for feeding natural gas to a burn ring within the flare and feeding the nitrogen/anhydrous ammonia misture to the burn ring.
In an embodiment of the present invention, the method comprises the steps of providing a blower for flowing air into the flare and blowing air into the flare via the blower to aid in the burning of the anydrous ammonia.
In an embodiment of the present invention, the method comprises the steps of visually looking for leaks in the container and providing a housing having a cover on the container having a plurality of valves therein and a plurality of sideports for access to the interior of the housing. The method further comprises sampling the interior of the housing via the sideport for a quantity of anhydrous ammonia via a chemical detecting instrument for leaks and removing the cover of the housing to inspect the interior of the housing for leaks.
In an embodiment of the present invention, the method comprises the steps of weighing the container and comparing the weight of the container to a tare weight of the container to determine a weight of the anhydrous ammonia therein.
In an embodiment of the present invention, the method comprises the steps of providing a nitrogen tank having nitrogen contained therein and attaching a nitrogen line between the nitrogen tank and a first valve of the container. The method further comprises the steps of heating a portion of the nitrogen line to heat nitrogen contained within the nitrogen line and attaching a flare line between the container and the flare.
In an embodiment of the present invention, the method comprises the steps of sampling a quantity of anhydrous ammonia in vapor form to determine a concentration of vapor within the container and verifying the identity of the anhydrous ammonia within the container.
In an embodiment of the present invention, the nitrogen gas is heated to between 100xc2x0 F. and 300xc2x0 F.
In an embodiment of the present invention, the method comprises the steps of inspecting the container for leaks via a leak detection apparatus and stopping the cleaning of the container if a leak is found having a concentration of at least 50 ppm.
In an embodiment of the present invention, the method comprises the steps of injecting the heated nitrogen into the container via a liquid valve on the container and venting the gas within the container to the flare via one of the valves.
In an alternate embodiment of the present invention, a method of cleaning a pressurized container is provided. The method comprises the steps of providing a pressurized container an amount of anhydrous ammonia wherein the container has a plurality of valves and injecting a quantity of heated nitrogen gas into the container to form a nitrogen/anhydrous ammonia mixture. The method further comprises venting the nitrogen/anhydrous ammonia mixture to a flare and repeating the injection of the container with the heated nitrogen gas and venting the mixture of the flare until the concentration of the anhydrous ammonia is at most about 50 ppm.
In an embodiment of the present invention, the method comprises the steps of inspecting the container for leaks.
In an embodiment of the present invention, the method comprises the steps of inspecting the container for leaks via a leak detection apparatus and stopping the cleaning of the container if a leak is found having a concentration of at least about 50 ppm.
In an embodiment of the present invention, the method comprises the steps of visually looking for leaks in the container and providing a housing having a cover and an interior space wherein a plurality of valves are contained within the interior space. The method further comprises providing at least one sideport in the housing for accessing the interior space of the housing, sampling the interior of the housing via the sideport for a leak in the plurality of valves via a chemical detection device and removing the cover to inspect the interior space of the housing for leaks.
In an embodiment of the present invention, the method comprises the steps of weighing the container and comparing the weight of the container to a tare weight of the container to determine a weight of the anhydrous ammonia therein.
In an embodiment of the present invention, the method comprises the steps of providing a nitrogen tank having nitrogen therein and attaching a nitrogen line between a nitrogen tank and a first valve of the container. The method further comprises heating a portion of the nitrogen line to heat nitrogen contained within the nitrogen line and attaching a flare line between the container and a flare.
In an embodiment of the present invention, the method comprises the step of sampling a quantity of anhydrous ammonia contained in the headspace of the container to determine a concentration of the anhydrous ammonia within the headspace.
In an embodiment of the present invention, the nitrogen gas is heated to between 100xc2x0 F. and 300xc2x0 F.
In an embodiment of the present invention, the method comprises the steps of injecting the heated nitrogen into the container via a liquid valve on the container and venting the nitrogen/anhydrous ammonia mixture within the container to the flare via a vapor valve on the container.
In an embodiment of the present invention, the method comprises the steps of injecting the container with steam after the concentration of the anhydrous ammonia therein is about 50 ppm, removing the pressure plate on the container and entering the container and cleaning debris from the container.
It is, therefore, an advantage of the present invention to provide a method of cleaning a pressurized container having a quantity of chemicals, such as, for example, AA, therein that safely and efficiently removes the chemicals from the container. Moreover, it is advantageous that the present invention removes the chemicals from the container without risking exposure to people or the environment.
Further, it is an advantage of the present invention to provide a method of cleaning a pressurized container having a quantity of chemicals therein that allows the chemicals to be removed without causing damage to the container by freezing the container or pipes connected thereto. In addition, an advantage of the present invention is that the heated nitrogen gas used to remove the product will not condense within the container and therefore will not mask the presence of the chemicals therein.
Another advantage of the present invention is to provide a method of cleaning a pressurized container having a quantity of chemicals therein that is largely automatic and therefore allows an individual to monitor the process without exposing the individual to the chemicals. Additionally, an advantage of the present invention is that a plurality of types of containers may be cleaned using the system and method defined herein, including, but not limited to, rail tank cars and other like containers.
Additional features and advantages of the present invention are described in and will be apparent from, the detailed description of the presently preferred embodiments and from the drawings.